Approximately 300 kg/day of food-grade CO 2 was injected through a perforated pipe placed horizontally 2-2.3 m deep during July 9-August 7, 2008 at the MSU-ZERT field test to evaluate atmospheric and near-surface monitoring and detection techniques applicable to the subsurface storage and potential leakage of CO 2 . As part of this multidisciplinary research project, 80 samples of water were collected from 10 shallow monitoring wells (1.5 or 3.0 m deep) installed 1-6 m from the injection pipe, at the southwestern end of the slotted section (zone VI), and from two distant monitoring wells. The samples were collected before, during, and following CO 2 injection. The main objective of study was to investigate changes in the concentrations of major, minor, and trace inorganic and organic compounds during and following CO 2 injection. The ultimate goals were (1) to better understand the potential of groundwater quality impacts related to CO 2 leakage from deep storage operations, (2) to develop geochemical tools that could provide early detection of CO 2 intrusion into underground sources of drinking water (USDW), and (3) to test the predictive capabilities of geochemical codes against field data. Field determinations showed rapid and systematic changes in pH (7.0-5.6), alkalinity (400-1,330 mg/l as HCO 3 ), and electrical conductance (600-1,800 lS/cm) following CO 2 injection in samples collected from the 1.5 m-deep wells. Laboratory results show major increases in the concentrations of Ca (90-240 mg/l), Mg (25-70 mg/l), Fe (5-1,200 ppb), and Mn (5-1,400 ppb) following CO 2 injection. These chemical changes could provide early detection of CO 2 leakage into shallow groundwater from deep storage operations. Dissolution of observed carbonate minerals and desorptionion exchange resulting from lowered pH values following CO 2 injection are the likely geochemical processes responsible for the observed increases in the concentrations of solutes; concentrations generally decreased temporarily following four significant precipitation events. The DOC values obtained are 5 ± 2 mg/l, and the variations do not correlate with CO 2 injection. CO 2 injection, however, is responsible for detection of BTEX (e.g. benzene, 0-0.8 ppb), mobilization of metals, the lowered pH values, and increases in the concentrations of other solutes in groundwater. The trace metal and BTEX concentrations are all significantly below the maximum contaminant levels (MCLs). Sequential leaching of core samples is being carried out to investigate the source of metals and other solutes.
EOS7C is a TOUGH2 module for multicomponent gas mixtures in the systems methanecarbon dioxide (CH 4 -CO 2 ) or methane-nitrogen (CH 4 -N 2 ) with or without an aqueous phase and H 2 O vapor. EOS7C uses a cubic equation of state and an accurate solubility formulation along with a multiphase Darcy's Law to model flow and transport of gas and aqueous phase mixtures over a wide range of pressures and temperatures appropriate to subsurface geologic carbon sequestration sites and natural gas reservoirs. EOS7C models supercritical CO 2 and subcritical CO 2 as a non-condensible gas, hence EOS7C does not model the transition to liquid or solid CO 2 conditions. The components modeled in EOS7C are water, brine, non-condensible gas, gas tracer, methane, and optional heat. The non-condensible gas (NCG) can be selected by the user to be CO 2 or N 2 . The real gas properties module has options for Peng-Robinson, RedlichKwong, or Soave-Redlich-Kwong equations of state to calculate gas mixture density, enthalpy departure, and viscosity. Partitioning of the NCG and CH 4 between the aqueous and gas phases is calculated using a very accurate chemical equilibrium approach. Transport of the gaseous and dissolved components is by advection and Fickian molecular diffusion. We present instructions for use and example problems to demonstrate the accuracy and practical application of EOS7C. 3Rev.
Reactive fluid flow and geochemical transport in unsaturated fractured rocks has been of increasing interest to investigators in the areas of geo-and environmental-sciences. To test geochemical hypotheses based on petrologic observation and to predict geochemical reactions that occur through a complex dynamic interplay of physical and chemical processes, we use the methods presented in a companion paper (part 1, this issue p. 16 -33) to investigate two problems: (1) supergene copper enrichment in unsaturated-saturated media and (2) predicted effects of thermohydrology on geochemistry during the Drift Scale Heater Test at the Yucca Mountain potential nuclear waste repository, Nevada. Through these two examples we address the importance of the following issues on geochemical processes: (1) participation of gas phase in transport and reaction, (2) interactions between fractures and rock matrix for water and chemical constituents, (3) heat effects on fluid flow and reaction properties and processes. In the supergene enrichment system, oxygen gas diffusion from the land surface through fractured rock promotes the alteration of the primary sulfide minerals and the subsequent deposition of secondary minerals. Modeling of the large-scale heater test shows effects of fracture-matrix interaction, heat-driven vaporizing fluid flow, and CO 2 degassing on mineral alteration patterns. The two examples also serve as a demonstration of our methods for reactive transport in variably saturated fractured rocks. introduction Reactive fluid flow and geochemical transport in unsaturated fractured rocks have been of increasing interested to investigators in the areas of geo-and environmentalsciences such as mineral deposits, contaminant transport, groundwater quality, waste disposal, acid mine drainage remediation, sedimentary diagenesis, and fluid-rock interactions in hydrothermal systems. This is a challenging issue because of the complexity of multiphase fluid flow, water-gas-rock and fracture-matrix interaction mechanisms, and difficulties dealing with physical and chemical heterogeneities and the strong non-linearities in the governing equations. For oxidized sulfide ore deposits, microscopic and petrologic studies based on 3-dimensional field mapping offer unique evidence as to the present state of surficial geochemical processes, mineral distribution, and controlling geological, hydrological, tectonic, and climatic factors (Brimhall, Alpers, and Cunningham, 1985;Ague and Brimhall, 1989). In fact, for almost a century supergene leaching and enrichment have been at the core of understanding redox processes at the paleo-ground water table. Geochronological methods cast such hydro-chemical systems in a temporal frame of reference so that an assortment of known deposits may be related in both a relative and absolute sequence of progressive geochemical states.The scientific relevance of numerical modeling of irreversible natural phenomena depends upon the character of the systems being modeled: natural or anthropogenic. In natural ...
SummaryECO2N V2.0 is a fluid property module for the TOUGH2 simulator (Version 2.1) that was designed for applications to geologic sequestration of CO 2 in saline aquifers and enhanced geothermal reservoirs. ECO2N V2.0 is an enhanced version of the previous ECO2N V1.0 module (Pruess, 2005). It expands the temperature range up to about 300 o C whereas V1.0 can only be used for temperatures below about 110 o C. V2.0 includes a comprehensive description of the thermodynamics and thermophysical properties of H 2 O -NaCl -CO 2 mixtures, that reproduces fluid properties largely within experimental error for the temperature, pressure and salinity conditions of interest (10 °C < T < 300 °C; P < 600 bar; salinity up to halite saturation). This includes density, viscosity, and specific enthalpy of fluid phases as functions of temperature, pressure, and composition, as well as partitioning of mass components H 2 O, NaCl and CO 2 among the different phases. In particular, V2.0 accounts for the effects of water on the thermophysical properties of the CO 2 -rich phase, which was ignored in V1.0, using a model consistent with the solubility models developed by Pruess (2005, 2010). In terms of solubility models, This report gives technical specifications of ECO2N V2.0 and includes instructions for preparing input data.
Contact : Eric S onnenthal, (5 10)48 6-5 8 66, elsonnen thal @ lbl. gov Research ObjectivesThe objectives of this study were to evaluate the thermal-hydrological-chemical (THC) effects on flow and geochemistry in the unsaturated zone (UZ) at Yucca Mountain at a mountain scale. The major THC processes important in the UZ are (1) mineral precipitatiorddissolution affecting flow and transport to and from the potential repository, and ( 2 ) changes in the compositions of gas and liquid that may seep into drifts. ApproachThe conceptual model developed for THC processes provides the basis for modeling mineral-water-gas reactions, as they influence the chemistry of water and gas and associated changes in mineralogy and hydrologic properties. Data incorporated in the model include hydrologic and thermal properties, geologic layering from the UZ 3-D flow and transport model, geochemical data (fracture and matrix mineralogy, water and gas geochemistry), and thermodynamic and kinetic data. Simulations included coupling among heat, water, and vapor flow; aqueous and gaseous species transport; kinetic and equilibrium mineral-water reactions; and feedback of mineral precipitatiorddissolution on porosity, permeability, and capillary pressure for a dual permeability (fracture-matrix) system. Simulations were performed using TOUGHREACT V2.3.The effects of coupled THC processes on the evolution of flow fields and water and gas chemistry in the UZ were evaluated for an above-boiling thermal operating mode. A cross section was chosen from the UZ 3-D flow and transport model that follows a north-south trend through the potential repository. Minerals include calcite, silica phases, feldspars, zeolites, clays, gypsum, fluorite, and iron oxides with the relevant aqueous species. The gas phase consists of air, water vapor, and CO2. The composition of the initial and infiltrating water was derived from the matrix pore water extracted from the Topopah Spring welded tuff near the ongoing Drift Scale Test. AccomplishmentsThe simulations revealed that by 5,00Oyears, most of the region above and directly below the potential repository undergoes a small reduction in fracture porosity of less than 1 percent (Figure 1). Above the northern edge, a region of slight porosity increase persists, owing to enhanced vapor convection and condensation. The areas that show the most effect as a result of heating are in the zeolitic units below the potential repository, where calcic zeolites dissolve to form alkali feldspars, leading to increased aqueous calcium concentrations and increased porosity. The predicted range in pH from 7 to 9 is linked to changes in gas-phase CO2 concentrations induced by heating of pore waters.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.